Document /_query locale parameter

Author: pquentin

specification/_doc_ids/table.csv

@@ -148,6 +148,7 @@ eql-syntax,https://www.elastic.co/guide/en/elasticsearch/reference/{branch}/eql-
 eql,https://www.elastic.co/guide/en/elasticsearch/reference/{branch}/eql.html
 esql-query,https://www.elastic.co/guide/en/elasticsearch/reference/{branch}/esql-rest.html
 esql-query-params,https://www.elastic.co/guide/en/elasticsearch/reference/{branch}/esql-rest.html#esql-rest-params
+esql-returning-localized-results,https://www.elastic.co/guide/en/elasticsearch/reference/{branch}/esql-rest.html#esql-locale-param
 evaluate-dfanalytics,https://www.elastic.co/guide/en/elasticsearch/reference/{branch}/evaluate-dfanalytics.html
 execute-enrich-policy-api,https://www.elastic.co/guide/en/elasticsearch/reference/{branch}/execute-enrich-policy-api.html
 expected-reciprocal,https://www.elastic.co/guide/en/elasticsearch/reference/{branch}/search-rank-eval.html#_expected_reciprocal_rank_err

specification/esql/query/QueryRequest.ts

@@ -57,6 +57,10 @@ export interface Request extends RequestBase {
      * Specify a Query DSL query in the filter parameter to filter the set of documents that an ES|QL query runs on.
      */
     filter?: QueryContainer
+    /*
+     * Returns results (especially dates) formatted per the conventions of the locale.
+     * @doc_id esql-returning-localized-results
+     */
     locale?: string
     /**
      * To avoid any attempts of hacking or code injection, extract the values in a separate list of parameters. Use question mark placeholders (?) in the query string for each of the parameters.